Detergent compositions containing metal discoloration inhibitors



Patented Nov. 18, 1952 UNITED s'rarss smear osrica h I} caress-Eur conrr rfr ons con'rsrgmo- METAL DISCOLOBATION-INHIBITO B John a. Schaefler,Wyoming, om. swimsa; The Procter 8: Gamble Company, lvorydaie. Ohio, acorporation of Ohio No Drawing. Application September 12, 1952, SerialNo. 309.38;

10 Claims. (Cl. 252-431) This invention relates to methods of inhibitinthe discoloration of metals by detergents and wetting agents and toimproved compositions of this type containing discoloration inhibitors.

Some detergent compositions and wetting agents have the undesirableproperty of causing discoloration of various metals and alloys. such forexample as copper, brass, German silver and the like. This eflect may benoticed when the metallic surfaces are exposed to aqueous solutions ofthe composition, or when wet bars of the detergent lie thereon. Thediscoloration may manifest itself as a. tarnished appearance uponkitchen ware, cutlery and household utensils resulting from dishwashing,for example. It is sometimes marked in soap dishes. constructed of thesemetals, which are exposed in bathroom or lavatory to the action of wetdetergent bars. The surface layer of the bar also in some cases becomesdiscolored, and at times this discolored surface layer becomes detachedfrom the bar and sticks to the metal surface.

The discoloration phenomena which I have described appear in generalwhen susceptible .metals, under sumciently drastic conditions ofconcentration. time and temperature. are exposed to aqueous systemscontaining the class of anionic synthetic detergents or wetting agentswhich may be described as high molecular ortion to a minor extent, butin the detergent'compositions herein claimed, 1. e. those containingcalcium-sequestering phosphates, the discoloration is rapid andparticularly pronounced during detergent use.

It is an object of this invention to provide means whereby suchdiscoloration of metals may be minimized or prevented. It is a furtherobject to provide new detergent and wetting compositions which havelittle or no tendency to cause discoloration or surfaces of copper.brass, German silver and like susceptible metals. It is a further objectto provide detergent compositions in bar form, which bars will not besubject to discoloration if kept in contact, while wet. with soap di hesor other surfaces 0! such metals. other objects will appear in thedescription which fo lows. I have found that the objectionablediscolorationphenomena which I have described in large measure bQ-QHIDIMM by incol'lwl'llmdn the detergent or wetting composition .ordissolving in the aqueous solutions thereof small amounts of certaindiscoloration inhibitors. These inhibitors are organic compounds anucleus selected from the gmup of metal 0! I and tautomers thereof,wherein X may be by Guanine Bensimidazoio on N/ 5-methyl benzimidasolo1mm h was a.

CH-Ng 3 LE 2-phenyl imidazole CH-NE 4methyl lmidazole noisily Xantbine NH-C 3,5-dimethyl pyrazole G-nitroindazole H CNg 4'benzyl pyrazoleCHa-C-NH N CHr- -CH 4,5-dim thyl pyrazole C H-NH HgCH-CH! 3-allylpyrazole Benzotriazole CH-NH 4-phenyl-1,2.3-triuzoie 1,2-naphthotriazole4-nitrobenzotriazole It will be perceived from these examples that mygroup of inhibitors includes a wide variety of compounds, since not onlyis variation possible in the members oi! the ring structure and theirpositions and bonding, but also a wide variety of substituents may beattached to the structures disclosed. The discoloration-inhibitiveproperties of the compounds are inherent in the recited structureshowever and persist (within the limitations discussed hereinafter)irrespective of the nature of the remainder of the molecule.

Some of the illustrative compounds are subject to sulionation orsulfation (the term "sulionate" being used generically herein todesignate the product of either of these reactions), thereby combiningwithin themselves structures which may both promote and inhibit metaldiscoloration, and such products I do not claim as discolorationinhibitors.

In order to be efiective, these inhibitors must be water-soluble, butthe solubility need not be higher than is required to produce inhibitingaction at the particular temperature in question In general, solubilitydecreases with increasing molecular weight, and while compounds of tinspecified structure having molecular weight above 250 are in some caseseffective, I find that mosi inhibitors which are useful in practicalapplications are of molecular weight less than 250.

Many inhibitors of my invention also vary ii emciency at difierenttemperatures for reason: which appear not to be attributable tosolubilit: relationships. In such cases excellent result: can beobtained by mixing the inhibitors. F0: example, good inhibition over awide range 0: temperatures may be obtained by'mixing an in hibitor whichis most efficient at low temperatur' zvith one which is most eflicientat high tempera ure.

The effectiveness and the water-solubility o the inhibitors may beaifected by the pH of the solution. Some of the inhibitors maybe moreeffective, others lesseflfective, at a high pH such as or 11 than at alower pH. By mixing ones which are most effective at high pH with oneswhich are most eifective at low pH, good protection may be obtained overa wide range of pH values. t

Partly because of considerations such as the above relative tosolubility, temperature and pH,

partly because of innate differences in efllciency among the inhibitorsthemselves, and partly also because of diiferences in the nature of themetal and of the discoloring agent, the quantity of inhibitor requiredfor effective action differs from case to case. In all cases thequantity required is small, 0.01 per cent by weight of the aqueoussystem against which the metal is to be protected being ample. Becausein some cases the effectiveness of a discoloration inhibitor maydecrease when an optimum concentration is exceeded, I

prefer in general to avoid using amounts of ini composition. This may bedone in conventional manner and at any time, for example by mechanicallymixing the constituents or by milling them in the presence of a littlewater. The invention is not limited as to the means or method ofincorporating the inhibitor nor as to the stage in the process ofmanufacturing the composition at which the incorporation takes place noras to the physical form of the resulting nondiscoloring composition. If,for example, the finished product is to be an essentially dry detergentpowder, flake or granule, the inhibitor may be incorporated anduniformly distributed in an aqueous paste containing the otheringredients and this paste may be spray-dried or roll-dried inconventional manner. In case milled detergent ribbons or bars aredesired, the inhibitors 5 may if desired be incorporated during themilling procedure. It will be understood that the composition containingthe inhibitor may be in liquid, paste, powder, flake, bar or any otherdesired form.

The amount of inhibitor to be'incorporated in the compositions of myinvention should be sufllcient to inhibit discoloration when the saidcompositions are used in the normal manner for the purpose for whichthey are intended. Thus experience has shown that when detergentcompositions comprising high molecular organic sulfonated detergents andcalcium-sequestering phosphates are used for laundering or dishwashingpurposes (inorganic salts such as sodium chloride and sodium sulfatebeing frequently present in such compositions), or when such detergentsor wetting agents are used in the textile industry, the concentration ofsuch composition in the solution rarely exceeds 1 per cent byweight,even in extremely hard water. Furthermore, as was previouslystated, the concentration of inhibitor required in the solution in orderto be efiective is usually less than 0.01 per cent by weight. In ordertherefore to have a detergent aoracos cost of such inhibitors. Forexample, most such surface active organic sulfonated products inhousehold use and many such detergents and wetting agents used inindustry contain considerable quantities of inorganic salts and/or othermaterials and reduced quantities of sulfonated organic matter. In suchcases I find that eflec- -tive discoloration inhibition is oftenattained with amounts of inhibitor equivalent to about 3 per cent orless by weight of the sulfonation product contained therein but notexceeding 1 per cent by weight of the total composition.

The surface active organic .sulfonation product may be any of a numberof different types, all of which are water-soluble salts which arecharacterized by having in their molecular structure a long chainlipophilic group of about 8 to about 24 carbon atoms and also either asulfonic acid radical or a sulfuric acid ester radical or mixtures ofsuch radicals, there being preferably only one such sulfonic acid orsulfuric acid ester radical per molecule.

Among such compounds are the water-soluble salts of the sulfuricreaction product of aliphatic monohydric alcohols of about 10 to about24 carbon atoms, and especially the water-soluble salts of sulfuric acidesters of normal primary aliphatic alcohols of about 10 to about 18carbon atoms, such as those derived by reduction of coconut oil, cohunekernel oil, coquito nut oil, murumuru nut oil, ucuhuba nut oil, ouricurioil, palm kernel oil, babassu oil or other oils of the coconut oilgroup, a group'of tropical nut oils more than half of the combined fattyacids of which are lauric and myristic. The sulfuric esters of highmolecular alcohols from other oils. fats and waxes, of high molecularunsaturated aliphatic alcohols, of high molecular branched chain primaryalcohols and of high molecular secondary alcohols may also be used inthe compositions of my invention.

Other sulfuric esters which may be present in the compositions hereincontemplated include water-soluble salts of sulfuric esters of polyhy-'dric alcohols incompletely esterified with high molecularmonocarboxylic acids such as soapforming fatty acids, cyclic acids suchas those of rosin and tall oil and naphthenic acids, and synthetic acidssuch as may be obtained by oxidizing parafiln hydrocarbons or petroleumor by hydrogenating carbon monoxide (sometimes referred to as theFisher-Tropsch process) or by oxidizing the saturated or unsaturatedhydrocarbons or oxygenated hydrocarbons resulting from this process.Specific examples of such detergents are the water-soluble salts ofsulfuric esters of fatty acid monoglycerides and monoglycolides, such asthe sodium salt of the coconut oil fatty acid mono-ester of1.2-dihydroxypropane-3-sulfuric acid ester, the sodium salt of thelauric acid ester of sulfated ethylene glycol, and the sodium salt ofthe oleic acid ester of sulfated diethylene glycol;

Similarly, water-soluble salts of ethers of high molecular normalprimary alcohols and low molecular hydroxy alkyl sulfuric acid estersmay be employed, such as the sodium salt of the coconut fatty alcoholmono-ether of glycerol monosul- Q furic acid, and the sodium of ethyleneglycol sulfuric acid.

Similarly, water-soluble salts higher fatty acid 'alkylolamides may beemployed. such as the. sodium salt .of sulfated babassu oil fatty acidglycerol amide or of sulfated lauric amide of monoethanolamine.

Similar-1y, water-soluble salts of alkyl esters of salt of lauryl etherof sulfated I sulfonated dicarboxylic acids, such as 2-ethyl I hexylester of sodium sulfosuccinate, or watersoluble salts of high molecularfatty acid monoesters of low molecular hydroxy alkyl sulfonic acids maybe employed, such as the sodium salt sulfonic acids (for example, sodiumsalt of the oleic acid amide of N-methyl taurine), watersoluble salts ofhigh molecular alcohol esters of sulfocarboxylic acids (for example,sodium salt of tetradecyl alcohol ester of sulfoacetic acid),water-soluble salts of low molecular sulfocar-- boxylic acid amides ofalkylolamine esters of high molecular fatty acids (for example, sodiumsalt of the sulfoacetamide of amino ethyl laurate), water-soluble saltsof high molecular alkyl aromatic sulfonic acids (for example, sodiumalkyl naphthalene sulfonate or the sodium salt of the sulfonic acidderived by sulfonating the condensation product of benzene and achlorinated kerosene fraction, such as represented by the formula SOaHin which It represents alkyl groups of from about 9 to about carbonatoms) and watersoluble salts of ethers of high molecular alcohols andlow molecular hydroxy alkyl sulfonic acids (for example, monolaurylether of 1,2-dihydroxypropane-3-sodium sulfonate, and" lauryl ether ofthe sodium salt of isethionic acid) may be employed.

The calcium sequestering phosphates have metal-discoloring propertieswhen used in water even in the absence of sulfonated detergents orwetting agents, and they markedly contribute to any discoloration causedby the surface active sulfonated products herein referred to, when usedin conjunction with them. Such contribution may assume importance whenthe amount of such calcium-sequestering phosphates exceeds about one percent of the total weight of the composition. In view of the rapid andintense discoloration characteristics of detergent compositionscontaining calcium-sequestering phosphates, substantial amounts ofchlorides and/or sulfates may be present in the composition withoutsubstantially accelerating the discoloration of the metal orsubstantially affecting the reduction in discoloration eifected by theinhibitors of this invention. By calcium sequestering phosphates I meanwater-soluble salts of phosphoric acids which are poorer in water ofconstitution than orthophosphoric acid, such as tetrasodiumpyrophosphate, pentasodium triphosphate (sometimes referred to oussolutions. I place "hexasodium tetraphosphate" and "hexasodiumhexametaphosphate" in quotation marks to indicate that the salts sodesignated may be mixtures rather than pure chemical compounds. Thetetraphosphate" to which I refer is that compound or mixture which isdescribed in U. S. Patent 2,031,827 and the hexametaphosphate" is the.glassy variety sometimes called Grahams salt which is described in U. S.Patent 1,956,515. The metal-discoloring compositions which are improvedby adding my inhibitors may vary widely in the relative proportions ofthe constituents. Thus the surface active sulfonated products inadmixture with 1 per cent or more of calcium sequestering phosphatesmentioned above are active discolorants. Also mixtures containing only 1or 2 per cent of the sulfonation product and phosphate, such as scouringpowders or kitchen cleansers, sometimes cause trouble. In general, myinhibitors find practical application when used with detergent orwetting mixtures ranging in composition from 1 per cent to 99 per centsulfonated detergent or wetting agent and from 1 per cent to 99 per centcalcium sequestering phosphate, and it will be understood thatconstituents other than these may also be present.

Thus the compositions of my invention consist essentially of a mixtureof at least 1% and not more than 98% by weight of the water solubledetergent, at least 1% and not more than 98% by weight ofcalcium-sequestering phosphate, and a discoloration inhibitor in anamount not exceeding 1 by weight of the total composition and less thanthe amount of the water soluble detergent but suflicient to inhibitdiscoloration as t'ripolyphosphate), hexasodium tetraphosof non-ferrouscoppery metals in contact with water and the composition.

The term consisting essentially of as used in the definition of theingredients present in the composition claimed is intended to excludethe presence of other materials in such amounts as to interferesubstantially with the properties and characteristics possessed by thecomposition set forth but to permit the presence of other materials insuch amounts as not substantially to affect said properties andcharacteristics adversely.

These discoloration inhibitors appear to .be particularly useful inprotecting certain easily discolored metals containing copper, such ascopper itself and copper-containing alloys such as brass and Germansilver which I shall refer to as non-ferrous, coppery metals, as well asarticles of such metals which are plated with imperfect coatings or worncoatings of non-discoloring metals, such for example as nickel orchromium. Itwill be understood that various inhibiting compounds havingthe structures previously described may vary in effectiveness from metalto metal.

The following examples, in which all parts are by weight, illustrate theeifectiveness of the discoloration inhibitors and ways in which Ipractice the invention, but it is to be understood thatthe examples areillustrative only and that the invention is not limited thereby but onlyby the terms of the appended claims.

Example 1 (18% nickel, 17% zinc and 65% copper) were partially submergedtherein for 3 hours at 120 F. A colored tarnish film soon appeared,golden at first and eventually becoming dark blue or purple. Similarsheets, similarly submerged in a 0.5% solution of a similar mixture towhich 0.1 part of 5-methyl benzimidazole had been added developed onlyslightly tarnished appearance.

Very similar results were obtained when in place of the sulfatedmonoglyceride of the above example there was substituted:

(a) the sodium salt of a sulfonated alkyl benzene in which the alkylgroup contained about 9 to about 15 carbon atoms, or

(b) the sodium salt of the sulfuric acid ester or normal primaryalcohols of about to about 1-8 carbon atoms, derived from coconut oil.

Very similar protective action is also shown when in place of thepentasodium triphosphate of the above examples there is substitutedtetrasodium pyrophosphate or a glassy "hexasodium hexameta phosphate.

Example 2 A detergent composition was prepared containing approximately54 parts of commercial tripolyphosphate consisting of a mixture of amajor proportion of pentasodium triphosphate and a minor proportion oftetrasodium pyrophosphate, 18 parts of the sodium salt of the sulfuricacid ester of coconut oil alcohols, 17 parts of sodium sulfate, andincluding small proportions of sodium carbonate, sodium chloride andother inorganic salts, and 8 parts of water.

Strips of brass and German silver as in Example 1 were suspended in a0.5% solution of this mixture, becoming tarnished like those of Example1 in the absence of a discoloration inhibitor. Strips similarlysuspended in a like solution to which 0.05 part of benzotriazole (basedon the weight of the detergent composition) had been added developedonly slightly tarnished appearance.

Protective action in similar tests has been found for 0.02% 3,5-dimethylpyrazole, 0.5% 6- nitroindazole or benzotriazole, 0.1% adenine,

guanine, 5-methylbenzimidazole, or benzimldazole, 0.5% xanthine or4-methyl imidazole, or 1.0% hypoxanthine, 1,2-naphthotriazole or 4-nitrobenzotriazole when added to detergent compositions such as that ofExample 2.

The composition of Example 2 is representative of commercial detergentscomprising a mixture of water-soluble calcium-sequestering phosphates,sodium sulfate and/or chlorides, and high molecular organic sulfonationproducts which possess pronounced detergent power. Particularlyefiicient compositions of this character comprise a mixture ofcalcium-sequestering phosphates consisting predominantly (often about75%) of pentasodium triphosphate but having a minor proportion (oftenabout 25%) of tetrasodium pyrophosphate, a sodium alkyl sulfate in whichthe alkyl chain is that of a normal primary aliphatic alcohol of about10 to about 18 carbon atoms, sodium sulfate in varying amount butcommonly at least 10% by weight of the total, and a discolorationinhibitor, the ratio of the weight of the sulfonation product to thephosphates being about 1:1 to about 1:5, and the inhibitor being presentin an amount not exceeding 1% by weight of the total composition, butsufficient to inhibit discoloration of metals when in contact with waterand said composition.

This application is a continuation-in-part of my 9ia ilrgplicationSerial No. 74,713, filed February 4, 1

Having thus described my invention, what I claim and desire to secure byLetters Patent is:

1. A surface active composition consisting. essentially of a mixture ofat least 1 per cent and not more than 98 per cent by weight of awatersoluble detergent that is a salt of ahigh molecular organicsulfonation product of a material having in its molecular structure along chain lipophilic group of from 8 to 24 carbon atoms; at least 1 percent and not more than 98 per cent by weight of a calcium-sequesteringphosphate and a discoloration inhibitor for non-ferrous, coppery metalswhich is a water-soluble organic compound of molecular weight notexceeding 250,'

having a nucleus selected from the group consisting of nuclei of theformulae the amount of said water-soluble detergent but sufilcient toinhibit discoloration of said metals when in contact with water and saidcomposition.

2. The composition of claim 1 wherein the inhibitor is adenine.

3. The composition of claim 1 wherein the inhibitor is 3,5 -dimethylpyrazole. Y

4. The composition oi claim 1 wherein the inhibitor is benzotriazole.

5. The composition of claim 1 wherein the detergent is a water-solublesalt of the sulfuric reaction product of an aliphatic monohydric alcoholof about 10 to about 24 carbon atoms.

6. The composition of claim 1 wherein the detergent is a waters-solublesalt of the sulfuric acid ester of primary straight chain aliphaticalcohols of about 10 to about 18 carbon atoms.

7. The composition of claim 1 wherein the detergent is a water-solublesalt of the sulfuric acid ester of alcohols derived from an oil of thecoconut oil group.

8. The composition of claim 1 wherein the detergent is a water-solublesalt of a suli'onic acid of the formula soar. 3

wherein R represents alkyl groups of about 9 to about 15 carbon atoms.

9. The composition of claim 1 wherein the detergent is a water-solublesalt of a sulfated monoglyceride of the formula cmosom HOH H10 0 C Rwhere RCO represents acyl groups of fatty acids of about 10 to about 18carbon atoms.

u 10.,The composition of china 1 wherein the calcium-sequesteringphosphate is a sodium salt.

The following references are of recbrd inthe me of this patent:

' 12 UNITED STATES PATENTS Number Name Date Chapman Aug. 12, 1930Shoemaker May 30, 1939 Keenen Apr. 15, 1941 Teeters Aug. 17, 1943 LindMar. 12, 1946 Blair Apr. 5, 1949

1. A SURFACE ACTIVE COMPOSITION CONSISTING ESSENTIALLY OF A MIXTURE OFAT LEAST 1 PER CENT AND NOT MORE THAN 98 PER CENT BY WEIGHT OF AWATERSOLUBLE DETERGENT THAT IS A SALT OF A HIGH MOLECULAR ORGANICSULFONATION PRODUCT OF A MATERIAL HAVING IN ITS MOLECULAR STRUCTURE ALONG CHAIN LIPOPHILIC GROUP OF FROM 8 TO 24 CARBON ATOMS; AT LEAST 1 PERCENT AND NOT MORE THAN 98 PER CENT BY WEIGHT OF A CALCIUM-SEQUESTERINGPHOSPHATE AND A DISCOLARATION INHIBITOR FOR NON-FERROUS, COPPERY METALSWHICH IS A WATER-SOLUBLE ORGANIC COMPOUND OF MOLECULAR WEIGHT NOTEXCEEDING 250, HAVING A NUCLEUS SELECTED FROM THE GROUP CONSISTING OFNUCLEI OF THE FORMULAE